Investigation Discovery's "Devil You Know" this week looks into another aspect of Chicago-area serial killer John Wayne Gacy: How his actions affected those who loved him.

Gacy, a successful Des Plaines businessman and community volunteer who performed at fundraising events dressed up as "Pogo the Clown," became known as one of the worst serial killers in American history when he was convicted of the murders of 33 young men and boys in the 1970s.

After his arrest in December 1978, Gacy pleaded not guilty by reason of insanity, but was convicted of all 33 murders by a Cook County jury and in March 1980, he was sentenced to serve 12 death sentences and 21 natural life sentences for the killings, all of which occurred between 1972 and 1978. He was executed by lethal injection at Stateville Correctional Center in Crest Hill in 1994 after years of appeals failed.

"Devil You Know" features interviews with Gacy's sister, Karen Kuzma, and her daughter, Sheri Hockenberry. Also interviews are Joseph Kozenczak and Dave Hachmeister, police officers who worked the case, and Gacy prosecutor Terry Sullivan. The hourlong episode doesn't delve too deeply into Gacy's motivations, focusing more attention on his family's reactions and continuing struggles with what he did.

The episode is likely to leave you wanting to learn more about the case and about his victims, most of whom are not even named..

In 1978, investigators found 27 bodies in a crawl space beneath Gacy's house at 8213 W. Summerdale Ave. in Norwood Park Township. Two other bodies were found buried on Gacy's property and four others were dumped into the Des Plaines River. As of 2011, seven of his victims remain unidentified.

"House of Horrors" explains how Gacy would lure his victims with job offers at his remodeling and construction business. He urged them to come to his home to sign work papers, then he killed them. All but one of his victims were strangled, according to the Chicago Tribune archives.

The "House of Horrors" episode of "Devil You Know" premieres at 9 p.m. CT Oct. 24 on Investigation Discovery. Here's what ID says about the episode:

Karen Kuzma was always close to her big brother. Fearful of their father's rage, the siblings bonded as children. When they grew older, Kuzma was proud of how her brother became a successful businessman and community volunteer when he performed at fundraising events dressed up as "Pogo the Clown." But when teenaged boys began disappearing off the streets of Chicago in the 1970s, Kuzma was doomed to a future of heartache. Police started to hone in on her brother, John Wayne Gacy, a monster who would become known as one of the worst serial killers in American history. Location: Des Plaines, IL

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